Typically, process-pumping applications in manufacturing facilities only require about two-thirds of a pump’s maximum rated capability.
For plants that run their pumps at full throttle, that represents an opportunity to save some money in energy costs.
The best way to do that is by reducing the speed and flow of the pump with a variable-speed drive, according to Mark Gmitro of Cary, N.C.-based ABB Group.
In a recent “MiHOW2” video presented by Motion Industries
, Gmitro demonstrated the difference in energy savings when using a valve to control the flow out of a centrifugal pump versus using a variable-speed drive to control the flow.
“Typically this would be used in process pumping, where a manufacturing facility has to move water throughout the plant,” Gmitro explained. “[In] a food-processing plant, they may have high-pressure wash-down systems, and they have to pump that water through the system at a specific pressure and volume of water.”
First, Gmitro simulated a pump operator restricting the water flow with a valve.
Gmitro showed that reducing the flow of a 40-gallon-per-minute pump to a rate of 30 gallons per minute cut the overall system efficiency to 16% and only produced a modest drop in annual energy savings.
“The pump is designed to run most efficiently at maximum flow,” Gmitro noted.
He then throttled the pump back to maximum flow, and showed that the system efficiency shot up to 36 percent.
In the second part of the demonstration, Gmitro reduced the water flow to 30 gallons per minute by slowing the motor with a variable-speed drive instead of restricting the flow with a valve. He noted that "the valve is still wide open."
While system efficiency was about 31 percent, the annual energy costs dipped below $400.
“So we have effectively cut our energy use by 50 percent while keeping system efficiency high and maintaining the process flow rate that is required,” Gmitro said.
Gmitro said the strategy works for larger pumps as well.
“As a matter of fact, the higher you are in horsepower, the quicker your payback will be,” Gmitro said. “Because a larger-horsepower motor will consume more energy and require more dollars to operate per year. So when you reduce the speed, your savings will be that much more, and your typical payback is far less time than a small-horsepower motor.”
Motion Industries recently launched the MiHOW2 video channel
“to share practical industrial applications—such as proper belt alignment—that viewers can adapt in their own facilities,” according to the company.